1. Field of the Invention
The present invention relates to a vehicle seat which is provided with a system for facilitating promoting of blood circulation in an occupant sitting on the vehicle seat for many hours, thereby facilitating relieving of fatigue of the occupant.
2. Description of the Related Art
There has been proposed a vehicle seat with fatigue reduction function, the vehicle seat having an occupant's body-motion promoting means provided in an interior of a seat back thereof (WO2007/094492). The occupant's body-motion promoting means is configured to intermittently perform repeated pressing/releasing operations with respect to the third lumbar vertebrae of an occupant on the seat times in a range of three to seven times, at a stroke amount in a range of 10 mm to 20 mm, and at a time interval of 5 minutes to 10 minutes.
The occupant's body-motion promoting means is provided as means to locally press the occupant on the seat under the above conditions. However, in the vehicle seat of the related art, when a vehicle in which the seat is employed is subjected to excessive acceleration applied laterally during travelling of the vehicle (hereinafter referred to as “lateral acceleration”) under a situation where a driver on the seat is repeatedly pressed locally by the occupant's body-motion promoting means, the driver is subjected to repeated pressure exerted by the body-motion promoting means and the lateral acceleration, so that it is feared that the upper body of the driver will become unstable, thus giving the driver an uncomfortable sitting feeling.
In the past, there was known a vehicle seat which is provided with a posture holding means in which a shape, hardness, etc. of a side air bag are adapted to be controlled by a lateral acceleration sensor in order to enhance lateral support of an occupant on the seat against excessive lateral acceleration (Japanese Patent Application Laid-Open Nos. H09-240399 and H11-278129).